A study published in the U.S. Dept. of Agriculture’s Amber Waves shows that the Supplemental Nutrition Assistance Program (SNAP) may reduce the number of recipient households with very low food security by about 38%. In addition, the study shows that the reduction may be as high as 59% for households that depend heavily on SNAP for their food purchases.

SNAP is the largest U.S. food assistance program, serving 46.6 million people monthly in fiscal year 2012. By providing eligible households with benefits to purchase food, SNAP stretches a family’s food budget and increases its food security, defined as consistent access to adequate food for active, healthy living.

Earlier research had shown that SNAP improves the food security of participating households, but uncertainty remained as to the extent of that improvement. This stems from the fact that the most food-needy households—those with less money or other resources for food or those more concerned about the quality or adequacy of their diets—are more likely to sign up for the program than other eligible households. This “self-selection” effect more than offsets the beneficial effect of the program, with the result that simple comparisons of current SNAP recipients with non-recipients generally find that SNAP recipients have worse food security than non-recipients with similar incomes.

This recent analysis sought to overcome the self-selection effect by comparing the food security status of current SNAP recipients with that of households that had recently left the program. This approach removes much of the self-selection effect because it inherently adjusts for unobserved characteristics that do not change at the time households leave the program. The difference of 8.9 percentage points in prevalence of very low food security between households that continued to receive SNAP benefits (14.2%) and households that had recently left the program (23.1%, after adjusting for their higher incomes and other more favorable conditions) provides an estimate of SNAP’s effectiveness in improving the food security of participating households.